Man's Conquest of Time
The history of the development of measuring of time is full of interest. The cave man measured time by making a grass rope with knots tied at equal intervals. He set fire to one end of it and measured the time by the burning from one knot to another. A few centuries later "Time Candles" were used, with notches at regular distances around them.
About the thirteenth century, a clock was evolved, deriving its name from the bells ("Glocken" or "cloches") used to strike the hours. Three centuries later the first watch was devised. It varied better than an hour a day. The selling price was the equivalent of fifteen hundred dollars in American money. They came to be known as watches because most night watchmen of the period carried them.
The next innovation came two centuries later. This was an invention of a hairspring made of pig's bristle. As time went on, the first watch factory was built in Switzerland, in the year 1840. In 1869 the output was still small despite the fact that there were thirty seven watch factories in the United States. These factories produced less than $5,000,000 worth of watches a year. Today, with the large factories in this country, the annual production is approximately $15,000,000. American made watches have taken their place in the forefront in production and quality.
New Clock to Stop Loss of Part Seconds
London. - The most accurate clock in the world which will not vary by more than a slight fraction of a second a year, has been made for the Royal Observatory at Greenwich.
It is an electric instrument and is being made especially by the National Physical Laboratory, which evolved and perfected the principle by which it works.
Pendulums Unreliable
Hitherto the standard clocks at Greenwich, which keep sidreal time and by which the mean solartime clocks are checked many times a day, have been pendulum instruments. These are liable to sudden small changes of rate, which are corrected by astronomical observations. In spell of cloudy weather, when observations cannot be made, these small errors may accumulate. It is only by keeping a constant watch on the comparison between the various standard clocks that this can be detected.
No Watch Necessary
The electric clock, once its accuracy is proved, will make much of this anxious watchfulness unnecessary. The special generator by which the clock is actuated produces an alternating current of 100,000 cycles a second, which is "demultiplied" electrically to provide a 500 cycle supply for the dial.
The generator is controlled by an oscillating quartz crystal contained in a chamber with a temperature kept constant to one-hundredth of a degree. The probable resultant margin of error is one in 100,000,000.
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